1. Field of the Invention
This invention relates to a liquid detection method and a liquid discharging device in which, in an ink-jet recording head used in a liquid discharging apparatus for recording (printing) characters and/or images by discharging ink droplets, a mechanism for detecting the remaining amount of ink within an ink tank for supplying ink to be discharged, and for determining continuity of ink from the ink tank to a portion near a discharging port, i.e., xe2x80x9cdisconnection of inkxe2x80x9d, is provided.
Recording (printing) is not necessarily performed on paper, but ink may be provided onto a recording medium such as cloth, string, film material, leather, metal, glass or the like.
More particularly, the present invention relates to a mechanism for detecting the state of ink used for recording in an ink tank for accommodating the ink, an ink channel for supplying a recording head with the ink, or a portion near a discharging port for discharging the ink.
2. Description of the Related Art
Recording apparatuses which utilize an ink-jet method of performing recording by discharging ink onto a recording material have been widely used due to ease of use.
An ink-jet recording apparatus includes an ink-jet head for discharging ink droplets, and an ink tank for accommodating ink to be supplied to the ink-jet head. The ink-jet head includes discharging ports for discharging the ink. A discharging-energy generation element for discharging the ink is provided near each of the discharging ports. A heating element for applying thermal energy to ink, a piezoelectric element for discharging ink by providing a mechanical pressure thereto, or the like is used as the discharging-energy generation element. The ink tank communicates with the discharging ports via an ink channel.
In the ink-jet recording apparatus, when ink within the ink tank decreases to a certain level, the ink cannot be supplied to the ink-jet head, so that normal discharge is disturbed and recording cannot be performed. Accordingly, in the ink-jet recording method, it is effective to provide a mechanism for detecting the remaining amount of ink and the absence of ink.
For example, the following methods for detecting the remaining amount of ink and a decrease in the remaining amount of ink have been known.
1. A method of detecting electric resistance and a state of conduction between two electrodes provided within the ink tank.
2. A method in which the ink tank is formed by a transparent material, an optical sensor is provided in the vicinity of the ink tank, and the presence of ink within the ink tank is detected by detecting the amount of light transmitted through the ink tank, or the amount of light reflected from a portion toward which the light is projected.
In order to detect the remaining amount of ink and a decrease in the remaining amount of ink, methods of detecting the presence of ink near the discharging ports have also been proposed. For example, the following method is disclosed in U.S. Pat. No. 4,853,718.
3. A method of detecting the electric resistance or the electrostatic capacitance between two electrodes provided in the vicinity of the discharging ports.
However, in method (1), in a recording apparatus in which the ink tank is exchanged by being separated from the head, when the remaining amount of ink in the ink tank becomes very small and the ink tank is replaced by a new ink tank, a portion relating to detection means, such as electrodes and the like, is also simultaneously replaced, thereby increasing the production cost of the ink tank, and the operating cost of the apparatus.
In method (2), a misoperation tends to occur due to stains on the surface of the ink tank or ink droplets adhered to the inner wall of the ink tank. In addition, a misoperation tends to occur in an ink tank having a light color, such as yellow.
In method (3), only ink near the discharging ports is detected, so that it is impossible to detect whether or not ink can be continuously supplied from the ink tank to the discharging ports, or the amount of ink within the ink tank.
When supplying ink from the ink tank to a discharging port of the ink-jet head, a bubble, in some cases, generates and grows in the liquid channel to the discharging port. When the bubble moves in accordance with the flow of ink and reaches the vicinity of the discharging port, the discharging port is filled with the bubble, even though the ink is present within the ink so as, to hinder the supply of the ink to the discharging port, thereby providing a state in which the ink is not discharged from the ink-jet head (this state will be hereinafter termed xe2x80x9cnondischargexe2x80x9d). During a printing operation, a recording dot corresponding to the discharging port where nondischarge has occurred is not recorded (this state will be hereinafter termed xe2x80x9cdot missingxe2x80x9d) thereby causing a failure in recording. Such a failure in recording causes degradation in the image quality. In addition, if it is necessary to perform another printing operation, a loss of time and useless consumption of an additional recording medium result. In addition, the element for generating the discharging energy of the ink-jet head may be forced to continuously generate the discharging energy in the of absence ink, thereby causing, in some cases, destruction of the element. Such a phenomenon in which the communication of ink from the ink tank to the discharging port is disconnected due to a bubble or the like is termed xe2x80x9cdisconnection of inkxe2x80x9d.
Such xe2x80x9cdisconnection of inkxe2x80x9d cannot be detected according to the above-described methods (1), (2) and (3).
In order to prevent xe2x80x9cdisconnection of inkxe2x80x9d, a method is considered, in which a recovery operation of sucking ink from the discharging port is automatically performed before recording or at a periodic timing. In this method, however, since an operation of sucking ink is performed even in the absence of disconnection of ink, the amount of consumption of ink which does not contribute to recording increases if ink is frequently sucked in order to prevent disconnection of ink, resulting in an increase in the operating cost per sheet. This method also results in an increase in the size of a unit for storing sucked ink, thereby hindering attempts to produce a small and light ink jet recording apparatus.
The present invention has been made in consideration of the above-described problems.
It is an object of the present invention to provide a liquid detection method and a liquid discharging device capable of detecting whether or not a liquid can be supplied from a tank for accommodating the liquid to each discharging port of a recording head in a case that a liquid channel from the tank to each discharging port is not disconnected by a bubble.
It is another object of the present invention to provide a liquid detection method and a liquid discharging device capable of detecting the remaining amount of a liquid within a tank for accommodating the liquid and a state in which the remaining amount of the liquid, is very small.
The present invention which achieves these objectives relates to a liquid detection method in a configuration including a tank for accommodating a liquid, and a recording head for discharging the liquid supplied from the tank via a liquid channel from discharging ports onto a recording medium. The method includes the steps of inputting a voltage having a predetermined waveform to a first electrode provided at a portion near the discharging ports, detecting a waveform of a voltage generated at a second electrode provided at a portion near the tank, and determining a presence of the tank, the remaining amount of the liquid within the tank, or continuity of the liquid from the tank to a portion near the discharging ports based on the detected waveform of the voltage.
In one embodiment, the liquid is an ink having a coloring component for the recording medium, or a liquid having a component which has electric conductivity.
In another embodiment, the first electrode contacts the liquid, and the second electrode is provided at a position where it does not contact the liquid due to an insulator for electrically insulating the second electrode from the liquid.
In still another embodiment, the first electrode is provided at a position where it contacts the liquid via a protective film for electrically insulating the first electrode from the liquid.
In still another embodiment, the distance from the first electrode to the ink and the area of a portion of the first electrode faces that the ink are within a range to cause electrostatic induction from the first electrode to the ink by the input voltage having the predetermined waveform.
In still another embodiment, the first electrode is provided at a position where it directly contacts the liquid.
In still another embodiment, the second electrode is provided at a position where it contacts the liquid via a protective film for electrically insulating the second electrode from the liquid.
In still another embodiment, an insulator for electrically insulating the second electrode from the liquid is provided between the liquid and the second electrode, and the second electrode does not contact the liquid.
In still another embodiment, the distance from the second electrode to the ink and the area of a portion of the second electrode that faces the ink are within a range to cause electrostatic induction from the second electrode to the ink by the input voltage having the predetermined waveform.
In still another embodiment, the recording head includes a plurality of electrothermal transducers for applying thermal energy to the liquid as discharging means for discharging the liquid from the discharging ports.
According to the above-described configuration, it is possible to detect the presence of the liquid in the tank or in the liquid channel from the tank to the discharging ports, and a state of disconnection of the liquid channel due to the presence of a bubble in the liquid channel.
By appropriately disposing the terminal for detection, it is also possible to detect the remaining amount of the liquid within the tank, as well as the mounting/detaching of the tank in the case of a configuration in which the tank can be separated from the recording head.
The present invention which achieves these objectives relates to a liquid discharging device including a tank for accommodating a liquid, and a recording head for discharging the liquid supplied from the tank via a liquid channel from discharging ports onto a recording medium. The device includes a first electrode provided at a portion near the discharging ports, a second electrode provided at a portion near the tank, detection means for inputting a voltage having a predetermined waveform to the first electrode and detecting a waveform of a voltage generated at the second electrode, and control means for determining a presence of the tank, a remaining amount of the liquid within the tank, or continuity of the liquid from the tank to a portion near the discharging ports based on the waveform of the voltage detected by the detection means.
In one embodiment, the liquid is an ink having a coloring component for the recording medium, or a liquid having a component reacting on the ink, which has electric conductivity.
In another embodiment, the first electrode is provided at a position where it contacts the liquid via a protective film for electrically insulating the first electrode from the liquid.
In still another embodiment, the distance from the first electrode to the ink and the area of a portion of the first electrode that faces the ink are within a range to cause electrostatic induction from the first electrode to the ink by the input voltage having the predetermined waveform.
In still another embodiment, the first electrode is provided at a position where it directly contacts the liquid.
In still another embodiment, the second electrode is provided at a position where it contacts the liquid via a protective film for electrically insulating the second electrode from the liquid.
In still another embodiment, an insulator for electrically insulating the second electrode from the liquid is provided between the liquid and the second electrode, and the second electrode does not contact the liquid.
In still another embodiment, the distance from the second electrode to the ink and the area of a portion of the second electrode that faces the ink are within a range to cause electrostatic induction from the second electrode to the ink by the input voltage having the predetermined waveform.
In still another embodiment, the first electrode contacts the liquid, and the second electrode is provided at a position where it does not contact the liquid due to an insulator for electrically insulating the second electrode from the liquid.
In still another embodiment, the first electrode and the second electrodes are provided at positions where they directly contact the ink.
In still another embodiment, the first electrode is maintained at a 0-level voltage except when detecting the ink.
In still another embodiment, the first electrode also operates as an electrode terminal used for driving or controlling the recording head.
In still another embodiment, the recording head includes a plurality of discharging means for discharging the liquid from the discharging ports, and the first electrode is an electrode, commonly connected to predetermined discharging means from among the plurality of discharging means, for driving the predetermined discharging means.
In still another embodiment, the recording head includes discharging means for discharging the liquid from the discharging ports, and the first electrode is an electrode grounded for driving the discharging means.
In still another embodiment, the recording head includes a plurality of discharging ports for discharging the liquid from the discharging ports, and the first electrode is an electrode, connected to each of the plurality of discharging means, for driving the discharging means.
In still another embodiment, the recording head includes an identifying terminal where a signal for identifying the recording head is input, and the first electrode also operates as the identifying terminal.
In still another embodiment, the recording head includes a plurality of electrothermal transducers for applying thermal energy to the liquid as discharging means for discharging the liquid from the discharging ports, and the first electrode comprises a protective member for protecting the electrothermal transducers.
In still another embodiment, the protective member is made of tantalum or tantalum oxide.
In still another embodiment, the second electrode is provided at a position adjacent to the tank so as to be horizontal with respect to a lower portion of the tank.
In still another embodiment, the second electrode is provided at a position adjacent to the tank in a vertical direction along a wall portion of the tank.
In still another embodiment, the second electrode is provided at a terminal between the tank and the recording head, and the control means determines a state of disconnection of ink in an ink channel between the terminal and the discharging ports.
In still another embodiment, the recording head includes a filter portion for filtering the liquid supplied from the tank, and the terminal is provided on the filter portion of the recording head, or on a joint portion between the tank and the recording head.
In still another embodiment, the device further includes a carriage for mounting the recording head and the tank, and scanning means for performing reciprocating scanning of the carriage relative to the recording medium. The second electrode is provided on a head holder unit for supporting the recording head, or on the carriage, or at a position of the liquid discharging device where the scanning by the carriage is not performed.
In still another embodiment, a plurality of the tanks and a plurality of the recording heads are provided so as to correspond to a plurality of liquids.
In still another embodiment, a plurality of the first electrodes and a plurality of the second electrodes are provided so as to correspond to the plurality of liquids.
In still another embodiment, a plurality of first electrodes are provided so as to correspond to the plurality of liquids, and the second electrode is integrally provided on the plurality of tanks at a position adjacent to the plurality of tanks.
In still another embodiment, a size of the second electrode substantially equals a width of the plurality of tanks.
In still another embodiment, the first electrode is provided commonly to the plurality of liquids, and a plurality of the second electrodes are independently provided for corresponding ones of the plurality of tanks.
In still another embodiment, the control means sequentially detects the plurality of liquids.
In still another embodiment, the tank is integrally configured with respect to the recording head.
In still another embodiment, the tank is configured so as to be separable from the recording head, and the tank and the recording head can be independently exchanged.
In still another embodiment, the device further includes display means for displaying a result of the determination by the control means.
In still another embodiment, the device is connected to host means capable of transferring data relating to recording, and a result of the determination by the control means is transmitted to the host means.
In still another embodiment, the device further includes recovery means for performing a recovery operation for the recording head, and the control means causes the recovering means to perform a recovery operation when the control means has determined that ink is discontinuous in the liquid channel from the tank to one of the discharging ports of the recording head.
In still another embodiment, the recording head includes a plurality of electromechanical transducers for applying discharging energy to the liquid as discharging means for discharging the liquid from the discharging ports.
In still another embodiment, the recording head includes a plurality of electrothermal transducers for applying thermal energy to the liquid as discharging means for discharging the liquid from the discharging ports.
According to the above-described configuration, it is possible to detect the presence of the liquid in the tank or in the liquid channel from the tank to the discharging ports, and to detect a state of disconnection of the liquid channel due to the presence of a bubble in the liquid channel. By appropriately disposing the terminal for detection, it is also possible to detect the remaining amount of the liquid within the tank, as well as the mounting/detaching of the tank in the case of a configuration in which the tank can be separated from the recording head.
According to the configuration of the present invention, it is possible to inexpensively detect a liquid, and to detect a liquid in each of tanks having various kinds of liquids, and liquids for a plurality of recording heads by the same means.
According to the configuration of the present invention, it is possible to detect even a liquid having a very light color as well as a transparent liquid without being restricted by the composition and the color of the liquid, and to perform detection in a very short time and without consuming the liquid.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.